I think I've figured out why social media folks have a bad "brand" in the business marketplace and amongst people who are not in that industry.  It really comes down to one word…

Execution (or lack thereof)

It's a loaded word — "execution" can mean different things for different people:

• following through on promises - there is just a high correlation of "social media expertise" to lack of follow-up.  I don't know what it is, but it's a real phenomenon.  I have encouraged my old friends at Microsoft to create a "social media certification" through Microsoft Learning like they do for developers.  The industry needs some third-party objectivity to help the rest of us figure out who can actually do things with social media.
• bringing business results, achieving milestones, ROI, etc. - social media is not quite yet mature enough today to create an obvious & measurable ROI in a wide range of cases — although you are starting to see some examples.  Progress in social media is measured today in a few things:  tactics to encourage sharing/virality, measuring success, starting and maintaining conversations, etc. This situation will improve dramatically, but right now success is still often times experimentation and setting the table for future opportunity.
• having expertise and the hustle necessary to get the job done - folks you meet in the social media business may know the buzzwords and the things that are necessary for success, but can they actually get you there?  I had a conversation with a real social media expert the other day who lamented to me "A lot of people call themselves experts because they know how to set up a Twitter account.  So what."  Therein lies the problem.  Other folks have the expertise, but they may not really have the time to help.  A lot of social media work can be labor-intensive — maintenance and monitoring of social media is a time-consuming process.

I don't think it helps that the very tools that social media experts purport to use are the very tools that can be used for blatant self-promotion.  So we all too often see "social media experts" as shameless self-promoters who lack substance and the ability to execute, all while claiming to be expert on a subject area where expertise is actually pretty darn hard to find and sometimes too subtle to notice.

It's really a shame — I know of good people in social media who really struggle with all the noise out there in the marketplace.  When you do find someone who knows what he/she is doing, that person is like gold because social media can help solve real business problems.  Unfortunately, finding good people is the hardest part of the problem for many corporations just because it's so hard to navigate all the nonsense.